Heat and mass transfer in a metal hydrogen reactor equipped with a phase-change heat-exchanger

Abstract

In recent years, storage of thermal energy has become a very important topic in many engineering applications and has been the subject of a great deal of research activity.The present paper deals with a latent heat storage system using phase change materials (PCMs) as an effective way of storing the released heat during hydrogen absorption process in a metal hydride reactor (LaNi5-H2), for recover it during desorption process. A transient two-dimensional mathematical model is developed for predicting the coupled heat and mass transfer within the hydride bed and the PCM. For this model, the liquid fraction in the PCM was described by an analytic approximation of the Heaviside step function which, to the knowledge of the authors, is applied at the first time to study phase change problems. The unstructured control volume finite element method was used to discretize the governing equations and a computer code was developed on Fortran 90 to solve the obtained algebraic equations. The validity of the numerical model has been performed by comparison with experimental data and several numerical simulations were carried out to evaluate the effect of some physical properties of the PCM on the hydriding and the melting processes.